1. Technical Field
Example embodiments generally relate to a fixing device and an image forming apparatus, and more particularly, to a fixing device for fixing a toner image on a recording medium and an image forming apparatus incorporating the fixing device.
2. Discussion of the Background
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having two or more of copying, printing, scanning, facsimile, plotter, and other functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of a photoconductor; an optical writer emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a development device supplies toner to the electrostatic latent image formed on the photoconductor to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the photoconductor onto a recording medium or is indirectly transferred from the photoconductor onto a recording medium via an intermediate transfer belt; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
Such fixing device may include a fixing rotary body heated by a heater and a pressing rotary body pressed against the fixing rotary body to form a fixing nip therebetween through which a recording medium bearing a toner image is conveyed. As the recording medium is conveyed through the fixing nip, the fixing rotary body and the pressing rotary body apply heat and pressure to the recording medium, melting and fixing the toner image on the recording medium.
The image forming apparatuses incorporating such fixing device are requested to be downsized and capable of forming the toner image on the recording medium quickly. To address this request, the fixing device may incorporate the fixing rotary body and the pressing rotary body that have a decreased diameter. However, the fixing nip formed between the smaller fixing rotary body and the smaller pressing rotary body may have a decreased length in a recording medium conveyance direction. As the recording medium is conveyed through the smaller fixing nip at an increased speed, the recording medium may receive a decreased amount of heat from the fixing rotary body that is insufficient to melt and fix the toner image on the recording medium precisely.
To address this circumstance, a pressurization lever may press the pressing rotary body against the fixing rotary body with increased pressure to form the greater fixing nip between the pressing rotary body and the fixing rotary body. However, a greater force may be required to isolate the pressing rotary body from the fixing rotary body.
To address this circumstance, a depressurization lever pivotable in accordance with a cover of the fixing device may be coupled to the pressurization lever. For example, as a user closes the cover, the depressurization lever causes the pressurization lever to press the pressing rotary body against the fixing rotary body. Conversely, as the user opens the cover, the depressurization lever causes the pressurization lever to isolate the pressing rotary body from the fixing rotary body. Accordingly, as the user closes and opens the cover with a reduced force, the pressing rotary body is pressed against and isolated from the fixing rotary body.
However, if the fixing device is installed in the downsized image forming apparatus, a pivot, that is, a fulcrum, of the depressurization lever about which the depressurization lever pivots as the cover is opened and closed is spaced apart from an effort point where the pressurization lever presses the pressing rotary body against the fixing rotary body and isolates the pressing rotary body from the fixing rotary body with a decreased distance therebetween. Accordingly, a force exerted by the user to open and close the cover may not be amplified. Consequently, the user may be requested to exert an increased force to open and close the cover, degrading usability of the fixing device.